diff --git a/app/controllers/projects/commit_controller.rb b/app/controllers/projects/commit_controller.rb
index b7f548e0e63..1d1184d46d1 100644
--- a/app/controllers/projects/commit_controller.rb
+++ b/app/controllers/projects/commit_controller.rb
@@ -23,8 +23,12 @@ class Projects::CommitController < Projects::ApplicationController
 
     respond_to do |format|
       format.html  { render }
-      format.diff  { render text: @commit.to_diff }
-      format.patch { render text: @commit.to_patch }
+      format.diff  do
+        send_git_diff(@project.repository, @commit.diff_refs)
+      end
+      format.patch do
+        send_git_patch(@project.repository, @commit.diff_refs)
+      end
     end
   end
 
diff --git a/changelogs/unreleased/zj-workhorse-commit-patch-diff.yml b/changelogs/unreleased/zj-workhorse-commit-patch-diff.yml
new file mode 100644
index 00000000000..bce68692d98
--- /dev/null
+++ b/changelogs/unreleased/zj-workhorse-commit-patch-diff.yml
@@ -0,0 +1,5 @@
+---
+title: Workhorse to send raw diff and patch for commits
+merge_request:
+author:
+type: other
diff --git a/lib/gitlab/git/commit.rb b/lib/gitlab/git/commit.rb
index fabcd46c8e9..d79a4dbeee4 100644
--- a/lib/gitlab/git/commit.rb
+++ b/lib/gitlab/git/commit.rb
@@ -342,21 +342,6 @@ module Gitlab
         parent_ids.first
       end
 
-      # Shows the diff between the commit's parent and the commit.
-      #
-      # Cuts out the header and stats from #to_patch and returns only the diff.
-      #
-      # Gitaly migration: https://gitlab.com/gitlab-org/gitaly/issues/324
-      def to_diff
-        Gitlab::GitalyClient.migrate(:commit_patch, status: Gitlab::GitalyClient::MigrationStatus::OPT_OUT) do |is_enabled|
-          if is_enabled
-            @repository.gitaly_commit_client.patch(id)
-          else
-            rugged_diff_from_parent.patch
-          end
-        end
-      end
-
       # Returns a diff object for the changes from this commit's first parent.
       # If there is no parent, then the diff is between this commit and an
       # empty repo. See Repository#diff for keys allowed in the +options+
@@ -432,16 +417,6 @@ module Gitlab
         Gitlab::Git::CommitStats.new(@repository, self)
       end
 
-      def to_patch(options = {})
-        begin
-          rugged_commit.to_mbox(options)
-        rescue Rugged::InvalidError => ex
-          if ex.message =~ /commit \w+ is a merge commit/i
-            'Patch format is not currently supported for merge commits.'
-          end
-        end
-      end
-
       # Get ref names collection
       #
       # Ex.
diff --git a/spec/controllers/projects/commit_controller_spec.rb b/spec/controllers/projects/commit_controller_spec.rb
index 694c64ae1ad..003fec8ac68 100644
--- a/spec/controllers/projects/commit_controller_spec.rb
+++ b/spec/controllers/projects/commit_controller_spec.rb
@@ -79,41 +79,18 @@ describe Projects::CommitController do
     end
 
     describe "as diff" do
-      include_examples "export as", :diff
-      let(:format) { :diff }
+      it "triggers workhorse to serve the request" do
+        go(id: commit.id, format: :diff)
 
-      it "should really only be a git diff" do
-        go(id: '66eceea0db202bb39c4e445e8ca28689645366c5', format: format)
-
-        expect(response.body).to start_with("diff --git")
-      end
-
-      it "is only be a git diff without whitespace changes" do
-        go(id: '66eceea0db202bb39c4e445e8ca28689645366c5', format: format, w: 1)
-
-        expect(response.body).to start_with("diff --git")
-
-        # without whitespace option, there are more than 2 diff_splits for other formats
-        diff_splits = assigns(:diffs).diff_files.first.diff.diff.split("\n")
-        expect(diff_splits.length).to be <= 2
+        expect(response.headers[Gitlab::Workhorse::SEND_DATA_HEADER]).to start_with("git-diff:")
       end
     end
 
     describe "as patch" do
-      include_examples "export as", :patch
-      let(:format) { :patch }
-      let(:commit2) { project.commit('498214de67004b1da3d820901307bed2a68a8ef6') }
-
-      it "is a git email patch" do
-        go(id: commit2.id, format: format)
-
-        expect(response.body).to start_with("From #{commit2.id}")
-      end
-
       it "contains a git diff" do
-        go(id: commit2.id, format: format)
+        go(id: commit.id, format: :patch)
 
-        expect(response.body).to match(/^diff --git/)
+        expect(response.headers[Gitlab::Workhorse::SEND_DATA_HEADER]).to start_with("git-format-patch:")
       end
     end
 
diff --git a/spec/lib/gitlab/git/commit_spec.rb b/spec/lib/gitlab/git/commit_spec.rb
index a05feaac1ca..2e068584c2e 100644
--- a/spec/lib/gitlab/git/commit_spec.rb
+++ b/spec/lib/gitlab/git/commit_spec.rb
@@ -554,24 +554,10 @@ describe Gitlab::Git::Commit, seed_helper: true do
     it_should_behave_like '#stats'
   end
 
-  describe '#to_diff' do
-    subject { commit.to_diff }
-
-    it { is_expected.not_to include "From #{SeedRepo::Commit::ID}" }
-    it { is_expected.to include 'diff --git a/files/ruby/popen.rb b/files/ruby/popen.rb'}
-  end
-
   describe '#has_zero_stats?' do
     it { expect(commit.has_zero_stats?).to eq(false) }
   end
 
-  describe '#to_patch' do
-    subject { commit.to_patch }
-
-    it { is_expected.to include "From #{SeedRepo::Commit::ID}" }
-    it { is_expected.to include 'diff --git a/files/ruby/popen.rb b/files/ruby/popen.rb'}
-  end
-
   describe '#to_hash' do
     let(:hash) { commit.to_hash }
     subject { hash }
diff --git a/spec/models/commit_spec.rb b/spec/models/commit_spec.rb
index 4e6b037a720..448b813c2e1 100644
--- a/spec/models/commit_spec.rb
+++ b/spec/models/commit_spec.rb
@@ -182,7 +182,6 @@ eos
     it { is_expected.to respond_to(:date) }
     it { is_expected.to respond_to(:diffs) }
     it { is_expected.to respond_to(:id) }
-    it { is_expected.to respond_to(:to_patch) }
   end
 
   describe '#closes_issues' do